FM Synthesis Ratio / Octaves

[ephyks]

Just a quick bit of information to those using fm8, and learning how to use the ratios properly.

Like myself, when I first picked up fm8, I used the same pitching I did in massive. Each 12 pitches was an octave, so I applied the same theory to fm synthesis. And for the longest time I could never figure out why all my synths sounded dissonant and off.

Well, to my surprise, they are not the same. Ratio and pitch are two entirely different things. So here's a chart to help you get everything in pitch when using fm synthesis.

I'll be using the root note of C4.

Note / Ratio
C4 = 1.000
C5 = 2.000
C6 = 4.000
C7 = 8.000
C8 = 16.000
C9 = 32.000
C10 = 64.000

Hope this helps all you fm8 and other fm synthesis users.

(These ratios are from fm8, other fm synthesizers might be a different.)

[Lektrone]

Nice post bro. Glad I ran across it

[GregoryTJ]

This works because each octave up is twice the pitch of the last octave. Think of the ratio as a frequency multiplier.

Your common pitch knob (course, semitone) adds to the base pitch instead of multiplying it.

Each octave has 12 keys. There are 12 semitones in an octave.

Each semitone is made of 100 cents (fine, tune.)

Hope this clarifies it a bit.